The present invention relates to a pneumatic tire capable of reducing the pass-by noise while maintaining the steering stability, wet grip performance and other running performances.
1. Field of the Invention
As the vehicle speed is getting faster along with the advancement of automotive technology in recent years, the vehicle running noise is increasing, and its control is demanded.
In the tread of the tire, a block pattern is formed by a plurality of circumferential grooves (a), (b) extending continuously in the tire circumferential direction and multiple lateral grooves (d), (e) crossing these circumferential grooves, and therefore, when running in rain, the water between the tread surface and the road surface is discharged through these grooves, and the wet grip performance is enhanced.
When such lateral grooves are provided in a multiplicity, the air compressed between the tread surface and road surface passes through the grooves suddenly, and it occurs intermittently, which causes noise called pumping noise. Such noise is often noted in the tire of block pattern comprising multiple lateral grooves.
To suppress such noise, it has been attempted to lower the speed of the air passing the lateral grooves by
1. decreasing the sectional area of the lateral grooves, PA0 2. bending the lateral grooves. PA0 (1) The noise frequency is dispersed and the noise is lessened by differing the pitch of blocks between the block rows. PA0 (2) The wet performance is enhanced by increasing the sectional area of the main grooves extending in the circumferential direction. PA0 (3) The turning performance is enhanced by setting the block pitch in the inner block rows larger than the outer block pitch so as to shape the outer block oblong while strengthening the grip force and brake performance. PA0 (4) The water discharging performance is enhanced and noise generation is further suppressed by smoothly continuing between the lateral grooves in the inner block rows and lateral grooves in the outer block rows.
or
By these measures, although the noise is slightly reduced, the measure 1 causes to lower the grip performance, especially wet grip performance, and the measure 2 causes uneven wear on the wall of the lateral grooves, thereby lowering the traveling performances and durability of the tire.
The present inventor has reached the invention by discovering that: